Influenza is a major public health problem. Approximately 30,000 people die annually in the United States from influenza1. Rates of influenza-related pneumonia, hospitalizations and deaths are higher among the elderly patients (>65 years of age). Influenza vaccination decreases complications, hospitalizations, and deaths 3, 4. However, it is also known that older patients are less well protected by the influenza vaccination than younger patients5,6. Therefore, this proposal addresses the critical need to develop novel treatments that will enhance antibody response to influenza vaccine to lessen influenza related morbidity and mortality. We propose to use a synbiotic, a combination of probiotic and prebiotic, as an adjuvant to improve the influenza vaccine antibody response among elderly patients in a randomized placebo-controlled trial. We hypothesize that the number of elderly patients who develop influenza protective antibodies will be higher and that antibody responses may be more rapid in onset in the AKSB arm than placebo. Antibody response against hemagglutinins of influenza A and B strains used in the 2006 vaccine will be studied. Probiotics are viable commensal microorganisms promote the establishment of beneficial microflora. Animal and human studies demonstrate that probiotics can up-regulate mucosal and systemic humoral and cell-mediated immune response to antigens. A prebiotic is a not digestible food ingredient that promotes growth of probiotic bacteria. Mayo Clinic in conjunction with Agri-King Corporation has developed a novel synbiotic called AKSB that contains a probiotic bacterium (Enterococcus faecium), a probiotic yeast (Saccharomyces cerevisiae), and a prebiotic (fructo-oligosaccharide [FOS]). Our phase I placebo-controlled trial of AKSB in normal human volunteers demonstrated that AKSB is safe and well tolerated. The investigators are currently conducting a randomized placebo-controlled trial to prevent travelers' diarrhea with AKSB. Our collaborative study group includes experienced infectious disease physicians, a vaccinologist, and statisticians. We have the infrastructure to successfully complete the proposed trial. We are in a unique position (because of the investigators experience, and infrastructure) to test this synbiotic to enhance the influenza vaccine antibody response in elderly patients, and therefore address a global health problem of particular relevance to this vulnerable population. If the hypothesis is proven, then synbiotics can be initiated for immediate use in this population and have profound public health significance during influenza epidemics or pandemics. Moreover, if the hypothesis is proven, then probiotics can be studied as adjuvants for other vaccines, to possibly prevent infections, and enhance immune function in select patient populations and to further study mechanisms of immune enhancement with commensal bacteria. [unreadable] [unreadable]